Basic Probability for TEAS Math
Probability measures how likely an event is to occur. Basic probability questions can often be solved by identifying the favorable outcomes and dividing by the total number of possible outcomes.
The Basic Probability Formula
For equally likely outcomes: Probability = Favorable outcomes ÷ Total possible outcomes For example, suppose a bag contains 5 blue balls and 3 red balls. There are: 5 + 3 = 8 total balls. The probability of selecting a red ball is: 3 ÷ 8 So the probability is 3/8.
Probability Can Be Written in Different Forms
A probability may be represented as: A fraction A decimal A percentage For example: 1/4 = 0.25 = 25% Being able to convert between these forms can be useful when solving math questions.
Probability of an Impossible Event
An impossible event has a probability of: 0 For example, if a box contains only blue cards, selecting a red card from the box would be impossible.
Probability of a Certain Event
An event that is guaranteed to occur has a probability of: 1 Or: 100%
Complementary Events
Sometimes it is easier to find the probability that something does not happen. The probability of an event not occurring can be found using: 1 − probability of the event occurring For example, if the probability of rain is 0.30, the probability of no rain is: 1 − 0.30 = 0.70
Read the Question Carefully
Probability questions often include extra information. Before calculating, identify:
- What outcomes are possible?
- Which outcomes are favorable?
- Are the outcomes equally likely?
- What exactly is the question asking for?
Final Takeaway
Basic probability becomes much easier when you identify the total possible outcomes and the favorable outcomes. Practice converting probabilities between fractions, decimals, and percentages.
